In one conventional form of aircraft comprising a helicopter, the propulsion of the aircraft is effected by means of a main rotor and an anti-torque rotor. Alternatively, the helicopter may utilize two main rotors without an anti-torque rotor.
The main rotor causes downward flow of air in the normal operation of the helicopter so as to direct at least a portion of the air adjacent the tail boom of the craft.
It is conventional in such aircraft to utilize internal combustion engines as the power source for the drive system. Such power systems have the serious disadvantages of being dependent upon depletable fossil fuel supplies. Further, such systems are affected by altitude and air temperature conditions so as to be limited in the full power ratings thereof.
Further, such internal combustion drive systems have the serious disadvantages of utilizing combustion air, requiring efficient ingestion thereof with attendant maintenance and failure problems.
Another serious disadvantage of the conventional internal combustion engines is the substantial engine noise generated in use.
Still another serious disadvantage is the formation of undesirable emissions aggravating the pollution problems.
Still another disadvantage of the present systems is the change in weight of fuel during operation so that the aircraft's center of gravity changes.
Still another disadvantage of the present systems is the relatively heavy weight of the engines, such as required by the mechanical transmissions utilized therewith.
Another disadvantage is in the relatively low efficiency of energy conversion. Still another disadvantage is the relatively high operating cost due to relatively short engine lifetime, high maintenance requirements, and relatively high initial cost.
Another disadvantage resides in the limitation on the torque capabilities of the internal combustion engines.